<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>案例-选项卡</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        ul,ol,li{
            list-style: none;
        }
        .box{
            width: 600px;
            height: 400px;
            border: 3px solid pink;
            margin: 50px auto;
            display: flex;
            flex-direction: column;
        }
        .box>ul{
            height: 60px;
            display: flex;
        }
        .box>ul>li{
            flex: 1;
            /* 占满剩余空间 */
            color: #fff;
            background-color: skyblue;
            font-size: 30px;
            display: flex;
            justify-content: center;
            cursor: pointer;
            /* 光标类型 */
            line-height: 60px;
        }
        .box>ul>li.active{
            background-color: orange;
        }
        .box>ol{
            flex:1;
            position: relative;
        }
        .box>ol>li{
            width: 100%;
            height: 100%;
            background-color: purple;
            display: flex;
            justify-content: center;
            align-items: center;
            color: #fff;
            font-size: 100px;

            position: absolute;
            left: 0;
            top: 0;
            display: none;
        }
        .box>ol>li.active{
            display: flex;
        }
    </style>
</head>
<body>
    <div class="box">
        <ul>
            <li class="active">1</li>
            <li>2</li>
            <li>3</li>
        </ul>
        <ol>
            <li class="active">1</li>
            <li>2</li>
            <li>3</li>
        </ol>
    </div>

    <script>
        //1.获取元素
        var btns=document.querySelectorAll('ul>li')
        var tabs=document.querySelectorAll('ol>li')

        //2.给btns里面所有按钮添加点击事件
        //forEach遍历数组 index索引
        btns.forEach(function(item,index){
            item.onclick=function(){
                //2-2，给btns和tabs里面的所有内容取消active类名（操作元素的类名）
                btns.forEach(function(t,i){
                    t.className=''
                    tabs[i].className=''
                    //tabs[i]数组
                })
              

            //2-3 当前点击的按钮和索引对应的盒子添加active类名（操作元素的类名）
            item.className='active'
            tabs[index].className='active'        
            }
        })

        //遍历数组
        // var res=btns.forEach(function(item,index){
        //     console.log(item)
        //     console.log(index)
        // })  
       
      
    </script>

</body>
</html>